Know your numbers!

Some say you should never fly IMC single pilot.

Others say they fly single handed down to minimums.

I personally subscribe to the group saying ‘know your limitations and fly within your limits’. One of my limitations is the amount of workload I can handle while flying IFR. So knowing that I always look for ways to limit it while flying.

One lesson I’ve learned just before my IFR checkride was to always, always have the airplane perfectly trimmed. I’ll be thankful to Nick for drilling that into me week before checkride forever. That saves you a bunch of wok right there – when the airplane goes where it need to go by itself you have time to fiddle with radios, maps and communicate.

This year in Oshkosh I’ve attended ‘single pilot IFR’ seminar and I’ve learned few more things there. One of them was ‘know your numbers’. Cruise, climb, descent power and attitude settings giving expected performance from your own airplanes make your work much, much easier. That comes even more important during instrument approaches. If you look closely at approach plates you can see that many of them have small table:

This table gives you pre calculated times between FAF and MAP at some predefined speeds. Arrow can fly 120kts on a good day, but sometimes it may be pushing it so I’ve decided to fly approaches at 90kts. One more reason for picking that speed is that when flying default approach 3 degree slope descent rate required to stay on the slope will be 480fpm. Very close to magic 500fpm that I was training to fly so many times.

So after all that information I’ve decided to go out there and find my numbers. Surprisingly I found out that Arrow doesn’t really want to slow down to 90kts and stay there. It took me a lot of pulling back before it settled down. After few minutes I found out that 2200rpm and 20″ gives me about 90kts.

Now on to descent. So time ago while reading various people’s description how they fly approaches I have noticed that many of them use gear to achieve desired descent rate at . It has one more advantage – when lowering gear at FAF is part of your procedure it’s very, very hard to miss that part and join the ‘belly up landing’ club. Intrigued by that I’ve tried that trick and lowered gear down when trimmed at 90kts. Sure enough the airplane started descent at almost 500fpm still keeping the same trimmed 90kts.

So summarizing, from now on my instrument flying procedure will look like this – after crossing IAF I’ll set up 20″mp and 2200rpm and gradually slow down to 90kts while flying intermediate part of the approach. Then when I’ll cross FAF I’ll lower the gear which will put me nicely on a glide slope without absorbing my brain too much. Also at this point the airplane will still be clean which allows to go missed with little to no changes in settings.

Now that I know those numbers it’s time to check them in practice. Stay tuned 🙂